Cook elbow macaroni according to package instructions. Make sure to salt your water for added flavor.
Once the pasta is al dente, drain the water and rinse pasta under cold water. Let the pasta drain thoroughly before proceeding to the next step.
While the elbow macaroni is draining combine the mayonnaise, sour cream, lemon juice, sugar, dijon mustard, onion powder, garlic powder, salt and pepper in a small bowl and whisk together.
Add the cooked macaroni, cooked chicken, green onion, red bell pepper, celery, and red onion to a large bowl.
Pour the mayonnaise mixture over everything and gently toss together until well-coated.
Store in an airtight container in the refrigerator for at least 1 hour to let it chill.